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Charm Semileptonic Decay. Jim Wiss Univ of Illinois HQL2004 June 2 , 2004. The importance of charm SL decay Pseudoscalar l n decay Vector l n decay Analysis of D K* mn The V/PS enigma : G (D+ K* mn / K mn) The D s fmn form factor enigma The future of SL decay - PowerPoint PPT Presentation
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1
Charm Semileptonic Decay
• The importance of charm SL decay• Pseudoscalar l decay• Vector l decay
– Analysis of DK*– The V/PS enigma: (D+K* / K– The Dsform factor enigma
• The future of SL decay– Cleo-c / Bes III (3770) running
Jim Wiss Univ of IllinoisHQL2004June 2 , 2004
Apologies for all the important and fascinating results that I had to skip
Featuring results from
2
Charm semileptonic decay as tests of LQCD
Apart from form factors, these decays can be computed using perturbation theory and are first order in CKM elements
The form factors incorporate hadronic complications and can be calculated via non-perturbative Lattice QCD.
(*)KD
c W l
q
scsV
Charm SL decays provide a high quality lattice calibration crucial to reducing future systematic error in the Unitarity Triangle. The same techniques validated in charm can be applied to beauty.
3
Pseudoscalar l decays
22 3
2 3
22 2
2(
4( ) )
F cq P
lf q O mG V Pd D P
dq
Provides a way to either measure CKM elements or to verify f+(q2) calculations
...But a major disconnect exists between experiment and theory. Theory works best where experiment works worse.
0 0.5 1 1.5 2 2.5 3
3P
2q
cleanest theory
highest rate
D l
2 2pole
1f
q m
2expf q ISGW
Two forms are used to parameterize f+(q2)
pole
These should be among the first unquenched lattice calculations... is easiest for LQCD
c
q
2max
2 qq s
q
l
lattice daughtera Kaon at rest in D frame
4
Comparing pole versus ISGW form in De
De should provide a powerful test of future lattice predictions
dp
dLattice
hep-ph/0101023
better sys as P0
Unfortunately present LGT offers very little discrimination between the two common forms
dp
d
P (GeV)
2q
22f q
...where differences are dramatic.e decay gets quite
close to the D* pole...
2 2 ( )q GeV
But past esignals have severe backgrounds and poor q2 resolution. Thus requiring parameterizations.
The lattice can now calculate f+ as a function of q2.
5
De/Ke
(0)0.86 0.07 0.05
(00.01
)K
f
f
Consistent w/ SU(3) breaking
32
2
2
2
2
324( )
F cq P
d D P
dq
G Pf
Vq
•Look for D*D decays. The “signal” is in the m plot.
•3 bins in q2 to get form factor info.
•Include peaking and non peaking backgrounds
0.082 .006 0.005 CLEOe
Ke
A big advance in precision!
Kl l
6
q2 information in De/Ke
MK
3
E691
Cleo
91
Cleo
93
E687 tag
E687 in
c
Cleo
04
1.4
1.6
1.8
2.0
2.2
2.4
2.6
Ke
nu
po
le m
as
s
The Cleo 04 epole mass is
After correcting for smearing Cleo reports these corrected q2 fractions
e
Ke
Clearly the data does not favor the simple Ds* pole
1.90 0.05
Disfavors ISGW2 form by ~4.2
7
Dvector decays
H0(q2), H+(q2), H-(q2) are helicity-basis form factors computable by LQCD...
A
22
22 2 2
20
0
sin sin(1 cos )sin
sin sin1( ) (1 cos )sin
8 2cos cos2sin cos
2cos
il Vi
l V il Vi
l l Vl V
l VV t
e He H
e Hmq m e H
q HH
H
c
c
cmc
q qq q
q qq q
q qq q
q
+
+ ---
-
ì üï ïï ïï ï+ï ïï ï+ï ïï ï= - - - +í ýï ï+ï ïï ï-ï ïï ï+ï ïï ïî þ
right-handed + left-handed +Two amplitude sums over W polarization using D-matrices
22 2
(0)( )
1i
iA
AA q
q M
22 2
(0)( )
1 V
VV q
q M
Helicity FF are combinations of the vector and two axial form factors
v 1(0) (0)r V A
2 2 1(0) (0)r A A
Two numbers parameterize the decay
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Interference in D+ K*
Yield 31,254
DataMC
K* interferes with S- wave K and creates a forward-backward asymmetry in the K* decay angle with a mass variation due to the varying BW phase
(2002)
F-B
asy
mm
etry
(m K
The S-wave amplitude is about 7% of the (H0) K* BW with a 45o relative phase
Focus “K*” signal
The same relative phase as LASS
matches model
-15% F-B asymmetry!
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K*form factors
1 cos 0.5V
0.5 cos 1V
0.5 cos 0.5V
acoplanarity
Results are getting very precise and unquenched calculations for incisive tests of the theory would be very desirable.
Incisive tests of the model are possible
Due to interference
10
Further tests of the K*model
Vcos
cos
Vcos
cos
Generally the model tracks the data rather well…
cos
A dramatic mismatch is seen at very low q2
suggesting a V(q20) problem
Focus even has a preliminary analysis of the K*0 line shape. K*0)is less than PDG by~1.6 MeV w/ errors
11
The vector/pseudo scalar enigma
K*l
/
K
E691
E653
Focus
Argus
Omega
Cleo 1
Cleo 2
Cleo 2
E687
0.3
0.4
0.5
0.6
0.7
0.8
0.9
muons electrons
0.620.02
*
0
Quark models predicted a
1
But V/PS 1/2 in data
oD KV
PS D K
The 2002 CLEO result tended to resolve this discrepancy by reporting a larger K*l/K2 BR
circa 1993Form factor ratios were well predicted but the scales were not.
The 2002 FOCUS result tended to reinstated it by getting a value close to previous K*l/K2 world average.
Direct (D+K* / K
*0
00.594 0.043 0.033
D K
D K
Use upstream Ks (~10%) so that both the numerator (K) and denominator (Ks ) leave 3 tracks in FOCUS -strip
0
0( ) ( ) (11 11) /K K
D D ns
0
0( ) ( ) ( 25 9.7) /K e K e
D D ns
sK
0CLEO(02) partially reflects a inconsistency in ( )D K e
0using (D K
*0 0D K l K l Theory
S-wave corrected
13
Ds form factor enigma
Theoretically the Dslform factor should be within 10% of D+ K*l The rV values were consistent but r2 for Dslwas 2 higher than D+ K*l
E7
91
CL
EO
E6
53
E6
87
BK
S
LM
MS
ISG
W2
0
0.5
1
1.5
2
2.5
3R
V
0
0.5
1
1.5
2
2.5
3
R2
circa 1999
ISG
W2
Fo
cus
E79
1
CL
EO
E65
3
E68
7 BK
S
LM
MS
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 1 2 3 4 5 6 7 8 9
RV
But the (2004) FOCUS measurement has consistent r2 values as well!
Ds versus D+ K*l
14
Other results on Ds
NO evidence for s-wave interference in Ds (<4%) of (H0 ) BW
Vcos cos
2qacoplanarity
Angular projections look finefo
cu
s
cle
o2
cle
o
arg
us
e687
0.2
0.4
0.6
0.8
0.540 0.040
BR relative to are consistent
A highly cut sample is required to remove backgrounds
15
The future of charm SL physics
“yellow book”1 fb-1MC
U = Emiss - Pmiss
Closing the neutrino in D e events
Cleo-c and Bes III: Run at (3770) with high luminosity and a modern detector
DoDo, DoK-+
K-
K+
+
Extremely clean events!
U = Emiss - Pmiss
prelimin data (60 pb-1)
Pavlunin
APS Talk
dp
d
P (GeV/c)
dp
d
P (GeV/c)
yellow book1 fb-1 (MC)
The q2 impasse afflicting SL data for the last 20 years should finally be overcome
16
Summary
Consistent FF for D+ K* & Ds
+
(m K
s-wave interferencein D+ K*
F-B
asy
mm
etry
V(q20) problem D+ K*
q2< 0.2
cos
New CLEO De/Keresult
0.082 .006 0.005 e
Ke
*( )sm D
(0)0.86 0.07 0.05
(0)K
f
f
*0
0
)
)
D K
D K
V/PS
ratio
17
dp
d
D e
1 fb-1 (MC)
U = Emiss - Pmiss
prelim dataSL Physics of the future
Promises of a rosy future with precision neutrino closure